The present invention relates to a mirror operating mechanism including a first mirror holding frame provided with a half-silvered mirror which splits light from the camera lens into a reflected portion and a transmitted portion and a second mirror holding frame provided with a totally reflecting mirror which reflects the light portion transmitted through the half-silvered mirror.
It is necessary for a mirror operating mechanism including a half-silvered mirror and a totally reflecting mirror used, for instance, in an automatic focus detecting device, to be reliable so that, during the observation of the object to be photographed through the viewfinder, light beams forming the image of the object to be photographed are simultaneously applied to a viewfinder optical system and to a focus detecting system so as to form the image of the object both on the focus detecting element of the focus detecting system and on the focusing screen of the viewfinder system. During the photographing operation, it is necessary for the mirror operating mechanism to retract the mirrors from the optical path between the photographing lens and the film surface to prevent the occurrence of a vignette effect on the film surface and to optically shield the light transmitting window of the half-silvered mirror when the mirror is lifted thereby to prevent the formation of ghost images attributed to the leakage of light from the viewfinder system and to reflections from the focusing screen. Furthermore, it is required to adjust the angle of the totally reflecting mirror in order to adjust the formation of an image on the focus detecting element.
In view of the foregoing, an object of the present invention is to provide a mirror operating mechanism which is simple in construction and yet which satisfies the above-described requirements.